Switching from metal components to resin components has recently been actively studied for the purposes of weight saving and cost reduction. The studies have led to practical use of vehicle components, industrial components, and electrical and electronic components formed from a thermoplastic resin, such as a polyamide resin, a polycarbonate resin, and a polyacetal resin. Also for use as sliding parts including gears and bearing retainers, replacement of metal sliding parts to resin sliding parts is currently in progress. Thermoplastic resins, however, are insufficient in wear properties or wear resistance properties, as the sliding parts are used under such conditions as a high load, a high temperature, and a high rotation speed. Thus, thermoplastic resins unfortunately may cause problems such as wear, fusion, cracking, and chipping.
Meanwhile, fluororesins are excellent in wear properties or wear resistance properties, heat resistance, chemical resistance, solvent resistance, weather resistance, flexibility, electrical properties, and other properties, and are thus used in various fields including cars, industrial machines, OA equipment, and electrical and electronic equipment. In particular, fluororesins have excellent wear properties or wear resistance properties, and are one of the resins having a notably low frictional coefficient. Many fluororesins, however, have inferior mechanical properties and physical heat resistance represented by, for example, deflection temperature under load compared to crystalline heat-resistant thermoplastic resins. Also, some fluororesins have inferior dimensional stability compared to amorphous heat-resistant thermoplastic resins. Hence, applications of fluororesins have been limited.
Under the above-mentioned circumstances, thermoplastic resins have been studied for the purpose of improving their wear properties or wear resistance properties and applying them to sliding parts in wider fields. For example, Patent Literature 1 discloses a resin composition containing 1 to 50 parts by weight in total of a fluororesin and graphite for each 100 parts by weight of a resin composition that consists of 60 to 99 parts by weight of a thermoplastic resin having a heat deformation temperature of 100° C. or higher and 40 to 1 part by weight of carbon fibers. Patent Literature 2 discloses a resin composition that contains a thermoplastic heat-resistant resin (A) having a molding temperature of 300° C. or higher, and a polymer (B) obtained by polymerization of fluoroacryl α-fluoroacrylate that has a specific structure as an essential component. Patent Literature 3 proposes a resin composition containing 70 to 99% by mass of a polyaryl ketone resin (A) and 30 to 1% by mass of a fluororesin (B), wherein the fluororesin (B) dispersed in the resin composition has an average particle size of 0.1 to 30 μm.
Patent Literature 4 proposes a resin composition containing a resin (component (A)) other than fluororesin and a fluororesin (component (B)). The resin composition has a sea-island structure where the fluororesin (component (B)), which constitutes the island phase, is dispersed in the resin (component (A)) other than fluororesin, which constitutes the sea phase, and also the island-phase fluororesin (component (B)) has an average particle size of 200 μm or smaller. Patent Literature 5 proposes a polyimide resin composition that substantially contains 1 to 40 parts by weight of a fluororesin having a melt flow index at 400° C. and 10 kg of 4.0 to 15.0 g/10 min for each 100 parts by weight in total of a resin composition consisting of a polyimide resin (40 to 95 parts by weight) having a specific repeating unit and a polyallyl ether ketone (60 to 5 parts by weight). Patent Literature 6 proposes a resin composition including an aromatic polyether ketone resin (I) and a fluororesin (II), wherein the fluororesin (II) is a copolymer of tetrafluoroethylene and a specific perfluoroethylenic unsaturated compound; the resin composition satisfies a ratio (I):(II) by mass between the aromatic polyether ketone resin (I) and the fluororesin (II) of 95:5 to 50:50; the fluororesin (II) is dispersed as particles in the aromatic polyether ketone resin (I); and the fluororesin (II) has an average dispersed particle size of 3.0 μm or smaller. Patent Literature 7 proposes a modified engineering plastic formed by cross-linking a mixture of an engineering plastic and a fluororesin. Patent Literature 8 proposes a thermoplastic resin composition containing 5 to 40 parts by mass of a fluororesin and 95 to 60 parts by mass of another thermoplastic resin, wherein at least part of the carbon atoms constituting the fluororesin molecular chain has a cross-linking structure with other carbon atoms constituting the molecular chain; and at least part of the fluororesin molecules has an active terminus.
Fluororesins are also known to be added to a thermoplastic resin for purposes other than enhancement of the wear properties or wear resistance properties. For example, Patent Literature 9 discloses a technique of improving the mold-processability, including decreasing the extrusion pressure and extrusion torque, in the mold-processing of engineering plastics. The technique includes adding 0.005 to 1% by mass of a fluoropolymer based on the total mass of the engineering plastics and the fluoropolymer. Patent Literature 10 discloses a technique of mixing PEEK resin fine powder in an aqueous dispersion of a PFA resin at a PFA:PEEK ratio by weight of 75:25 to 70:30, directly applying the resulting dispersion to a roughened metal surface in accordance with common methods, and baking the resulting product, so that a PFA-PEEK composite coating film having adhesion durability is formed. Patent Literature 11 discloses a thermoplastic resin composition containing a mixture of polyaryl ketone resin and thermoplastic fluororesin, wherein the thermoplastic fluororesin constitutes a continuous phase of the mixture and the polyaryl ketone resin constitutes a dispersion phase thereof. Patent Literature 12 proposes a polyaryl ketone film as a material for providing a film having a high Young's modulus, low dielectric constant, excellent flame retardancy, heat resistance, and insulation properties, and high rigidity, and a FPC including this film as the substrate thereof. The polyaryl ketone film includes a resin composition containing polyaryl ketone and another thermoplastic resin in an amount of 3 to 30 parts by weight for each 100 parts by weight of the polyaryl ketone. The film has a cushion rate of 3 to 30% and is stretched in at least one direction.